[Vibrant Android Development] BruceElliott:
I call this the "Gerald Ford" GPS fix, because it cannot walk and chew gum at the same time. (No offense intended to friends or relatives of the now-deceased Gerald Ford. He was a great man, and did a good job following the Nixon debacle.) However, he did acquire a reputation for not handling multitasking very well.

I walk on the top level of the parking garage at my office for exercise. I typically turn on GPS and Google's "My Tracks," mainly to keep track of the distance and time that I walk. I also turn on Pandora, BeyondPod, or Internet video news.

Attached below are screenshots showing testing results for S.gps.zip on these walks. JPEG 823 is a track record for the stock GPS in KA7 (completely stock KA7 PDA, modem, and kernel). (Note: Hover mouse over thumbnail to see JPEG number.) As you can see, while not perfect, the pattern is fairly tight. I walk along the inner-most ends of the outer set of parking space strips. You can see that quite nicely on the left side of the parking surface. The right side of the parking surface is always less accurate. I believe that is due to the fact that the 16-story office building where my office is located is about 50 m to the right of the screen shot. So, I may be in the shadow of one or more of the birds that I am locked onto when walking on that end of the parking garage surface. In any case, you can even see my walking up and back down the ramp leading up to the top parking surface.

JPEG 424 is a short walk using S.gps. These tracks are not too bad until I turned on Pandora, at which time S.gps took me to never-never land. JPEGs 148 and 219 are S.gps tracks taken while either listening to Pandora or watching a video newscast.

Although YMMV because every system is different, my conclusions and hypotheses, at least for my system and likely for other posters in this thread who have indicated the activity that they were testing with, are as follows:

S.gps is clearly extremely sensitive to other processes executing. I did not do enough testing to determine whether this sensitivity is related to CPU activity in general or to Internet activity specifically. If the former, it may be that the files and settings associated with S.gps configure the GPS chip to generate interrupts at a faster rate than the SGS processor can service. This could be the case if S.gps came from a tab with a faster processor, for example. So configuring the GPS chip on a system designed to handle a faster rate of interrupts could be expected to result in greater accuracy. However, doing this with a processor that cannot handle such interrupt stream might well result in decreased accuracy as many of the GPS measurements fail to make it into the kernel due to discarded interrupts. That would be consistent with the accuracy going to hell in a hand basket when the processor gets busy as a consequence of running processor-intensive apps, as I experienced.

That is just a wild educated guess. I asked Jellette a couple of times what S.gps does and how it does it, but got no response. In that Jellette is generally good about answering questions, it may be that he simply picked up the files somewhere and therefore does not know what the files and settings associated with S.gps are really doing. I also asked him how to back out of S.gps and received no answer. So, I wound up doing the old "Froyo that does not brick"---> JFD--->stock KA6 routine. (I did KA6 this time for maximum compatibility with the OverStock kernel.)

It is not my intention to beat up on Jellette here, rather to beat up on my results with S.gps. Goodness knows Jellette has done a world of good for this community through his sacrifice of time and effort. I am simply calling a spade a spade here as regards the performance of S.gps in my case, and also potentially validating what appears to be results experienced by others who have posted in this thread. I doubt that Jellette is interested in playing "The King's New Clothes" here.

One other comment as regards GPS testing. Conclusions derived from acquiring a fast fix on many satellites from the sofa should probably be taken with a grain of salt. After all, presumably you already know where your sofa is located.:rolleyes: Repeatability along a fixed path is the name of the game.